1. Technical Field
The present invention relates generally to an improved data processing system and in particular to a method and apparatus for processing methods in a data processing system. Still more particularly, the present invention relates to a method and apparatus for avoiding function activation and interpretation overhead for calls to common, trivial Java methods in a Java virtual machine interpreter.
2. Description of Related Art
Java is an object oriented programming language and environment focusing on defining data as objects and the methods that may be applied to those objects. xe2x80x9cJavaxe2x80x9d is a trademark of Sun Microsystems, Inc. Java supports only a single inheritance, meaning that each class can inherit from only one other class at any given time. Java also allows for the creation of totally abstract classes known as interfaces, which allow the defining of methods that may be shared with several classes without regard for how other classes are handling the methods. Java provides a mechanism to distribute software to different computing platforms.
Java is able to support applications for many types of data processing systems, which may contain a variety of central processing units and operating system architectures. The Java Virtual Machine (JVM) is a virtual computer component that resides only in memory. The JVM allows Java programs to be executed on different platforms as opposed to only the one platform for which the code was compiled. Java programs are compiled for the JVM. In this manner Java is able to support applications for many types of data processing systems, which may contain a variety of central processing units and operating systems architectures. To enable a Java application to execute on different types of data processing systems, a compiler typically generates an architecture-neutral file format. The compiled code is executable on many processors, given the presence of the Java runtime system. The Java compiler generates bytecode instructions that are non-specific to particular computer architectures. A bytecode is a machine independent code generated by the Java compiler and executed by a Java interpreter. A Java interpreter is a module in the JVM that alternatively decodes and executes a bytecode or bytecodes. These bytecode instructions are designed to be easy to interpret on any machine and easily translated on the fly into native machine code.
A development environment, such as the Java Development Kit (JDK) available from Sun Microsystems, Inc., may be used to build Java bytecode from Java language source code and libraries. This Java bytecode may be stored as a Java application or applet on a Web Server, where it can be downloaded over a network to a user""s machine and executed on a local JVM.
When extra speed in executing a Java program is needed, a Just In Time (JIT) compiler may be used to translate bytecodes for a method or class into native machine instructions before executing them. Typically, this compilation only occurs once per method. Some JIT compilers may compile entire classes, rather than one method at a time.
When a JVM interpreter encounters an invoke bytecode, the JVM interpreter locates the appropriate method to be called and then calls the method. This calling of the method may be performed by locating a method block and branching to the invoker for the method. The method block identifies the invoker and is a per method data structure. The invoker performs the function activation and interpretation and creates a stack frame for the target method. This process performed by the invoker involves insuring that parameters are passed appropriately to the target method. A monitor, also referred to as a lock, is obtained by the invoker if the method is synchronized. Other housekeeping chores may be involved based on the particular target method.
During the course of interpretation of bytecodes, when an invoke bytecode for a method is encountered, the interpreter will branch to the invoker whose address is specified for the method. The invoker for a method goes through a standard function activation and interpretation, creating a frame and beginning to interpret the methods of the bytecode. Often times, methods are called by Java programs in which the methods perform trivial tasks. These method calls incur the complete overhead of a method invocation including the creation and destruction of a function activation frame and method interpretation. This overhead is significant for these small or trivial methods.
Therefore, it would be advantageous to have an improved method and apparatus for avoiding function activation and interpretation overhead for calls to selected methods in the JVM interpreter.
The present invention provides a process in a computer for processing a method that performs a function. A determination is made as to whether the method is to be executed normally when the method is loaded. Responsive to an absence of a determination that the method is a method to be executed normally, instructions native to the computer are associated with the method by modifying the invoker pointer, wherein the instructions perform the function.